Devices for measuring forces in response to capacitor plate movement are shown in U.S. Pat. No. 3,911,738, issued to Fischer. As a force displaces the movable capacitor plate, a responsive displacement signal generates differential electric pulses that indicate the amplitude of the force being measured and that, when applied to the capacitor, electrostatically oppose the force and urge the movable plate toward its original position.
This device uses a capacitive bridge circuit to measure voltage level changes caused by deflection of the plate. When the electrostatic counterbalancing force is generated to restore the plate position, displacement may be reduced by the generated counterbalancing force which may be reduced by electronic signal compensation.
With the use of analog voltage levels, the movable plate should be sufficiently large to generate a detectable signal difference for small displacements. Furthermore, relatively expensive conventional hybrid technology is typically used to fabricate the force-sensing elements.